View of The Lece-Chalkidiki metallogenic zone: geotectonic setting and metallogenic features

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The Lece-Chalkidiki metallogenic zone: geotectonic setting and metallogenic features

Todor SERAFIMOVSKI

Faculty of Mining and Geology Stip, Goce Delcev 89, 9200 Stip, Republic of Macedonia Key words: Lece-Chalkidiki metallogenic zone, volcanogene-intrusive magmatism, polimetallic mineralization

Ključne besede: Lece-Chalkidiki metalogena cona, vulkanogeno-intruzivni magmati- zem, polimetalna mineralizacija

Abstract

Several characteristics define the contours of this significant metallogenic zone developed owing to post collision tectonomagmatic processes along the contact between the Vardar zone and Serbo-Macedonian massif (SMM): regional and local fracture structures, surface manifestations of the Tertiary volcanogene-intrusive magmatism and polymetal- lic mineralization styles (Pb-Zn, Cu, Au, Sb, As). The most striking are the fractures of NNW - SSE strikes as well as ring-radial ones typical of the volcanic structures (Leče, Zletovo, Pontokerasia). The absolute age of the calc-alkaline volcanic complexes ranges from 37 to 16 m.y. The strontium ratios for these magmatic rocks indicate a contamination of magma by material from the Continental crust (⁸⁷Sr/^a6Sr 0.706318 - 0.706928). Ore deposits are grouped into several metallogenic districts and ore fields each characterized by specific styles of mineralization and a mineral/elemental association.

Kratka vsebina

Lece-Chalkidiki metalogeno cono, ki je nastala kot posledica post kolizijskih tektono- magmatskih procesov na stiku med Vardarsko cono in Srbsko-makedonskim masivom določajo regionalni in lokalni prelomi, vulkanogeno-intruzivne strukture in polimetalno orudenje s Pb in Zn, Cu, Au, Sb ter As. Najbolj značilni so v smeri NNW - SSE potekajoči prelomi in obročaste vulkanske strukture Leča, Zletova in Pontokerassia. Absolutna sta- rost kalcijsko-alkalnega magmatizma, s katerim so v zvezi omenjene vulkanske strukture, je od 16 do 37 milijonov let. Izotopska sestava stroncija - razmerje ^8,Sr/⁸⁶Sr , ki je v območju od 0.706318 do 0.706928, kaže na kontaminacijo magme z materijalom iz konti- nentalne skorje. Rudna ležišča so vezana za različne metalogene province ter rudonosna območja s specifično mineralizacijo in mineralno ter elementno asociacijo.

Introduction

The Lece-Chalkidiki metallogenic zone is situated in the marginal parts between the Vardar zone in the west and the Serbo- Macedonian massif (SMM) in the east. It represents an elongated metallogenetic unit starting with the Leče ore district in the N-

NW, extending through the Kratovo-Zleto- vo, Buchim and Kilkis to the Eastern Chal- kidiki ore districts in the S-SE. After this ore district, the zone under consideration, along with the Vardar zone, buries into the Aegean Sea and bends to Izmir in the east.

It can be traced for over 700 km along strike with average width of 30 km (Fig. 1).

https://doi.org/10.5474/geologija.1999.010

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Serbo-macedoman metallogenic province

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Fig. 1. Geotectonic and matallogenic position of the Lece-Chalkidiki zone

1. Neogene volcanics; 2. Tertiary intrusives; 3. Neogene granitoids; 4. Jurassic grano-diorites; 5.

Hereynian granites; 6. Boundary of metallogenic provinces; 7. Boundary of metallogenic zones;

8. Lineaments

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Lead and zine are the dominant metals, followed by copper, gold, silver, antimony, arsenic and locally molybdenum. Uranium, PGE, bismuth and mercury also occur locally, but are less abundant.

Hydrothermal volcanogenic type of mineralization is most widespread - veins, stockwork-disseminated, and metasomatic (carbonate-hosted) deposits. Porphyry copper mineralization is related with subvolcanic and/or minor hypabyssal intrusions.

Skarn type mineralization (mainly with magnetite and sulphides) occurs sporadi- cally. Data about latest structural, magmatic, lithostratigraphic and metallogenetic characteristics which spatially belong to the Lece-Chalkidiki metallogenetic zone can be found in the papers of several au- thors. Among the first, mention should be made of those of Papadakis &

Michalidis (1976), Arsovski &

Ivanov (1977), J a n k o v i c etal.(1980).

However, detailed data, in terms of the metallogeny of the unit, are given by Serafimovski (1993).

Geotectonic setling

The Lece-Chalkidiki metallogenic zone developed along two regional tectonic units, the Vardar zone and the SSM.

The Vardar zone is a suture zone that developed following the closure of a branch of Tethyan ocean by Late Jurassic-Early Cre- taceous times.

The SMM is a rigid tectonic block situated west of the Carpatho-Balkanides. The SMM may have been prior to the Cretaceo- us period an island are, then welded with the Carpatho-Balkanides. It consists of Precambrian schists developed in two units-the Lower and Upper Complex. Such a tectonic environment was cut, during the Tertiary period, by several deep-fractured zones, striking mainly NNW-SSE. Calc-alkaline magmas penetrated along these regional dislocations at intervals, locally for- ming large volcano-plutonc complexes. The Lece-Chalkidiki metallogenic zone is asso- ciated with such structural-magmatic environment.

Regional dislocation controlled the position of the metallogenic zone and the volca-

no-plutonic complexes. The distribution of ore fields and individual deposits are mainly controlled by volcanic centers and lo~

cal dislocations.

The parent magma was derived from the lowest level of Continental crust, above the upper mantle. The collision between the Afričan and the Eurasian plates resulting in thickening of the Continental crust and its partial melting within the post-colision zone yielded calc-alkaline magmas. The strontium ratios indicate a contamination of magma by material from the Continental crust (Table 1).

Table 1. The strontium ratio in the volcanics from Lece-Chalkidiki zone.

Locality ⁸⁷Sr/⁸⁶Sr (%) ⁸⁷Rb/⁸⁶Sr (%) Zletovo 0.706318 0.4087 Borov Dol 0.706897 0.1246 Bučim 0.706928 0.2908 Damjan 0.706633 0.1459

The REE data may indicate similarities of igneous rocks in the Lece-Chalkidiki zone with those related with active Continen- tal margin (Serafimovski, 1993).The absolute age of this magmatism is in the range between 37.5 my and 16 my (Tables 2, 3).

Metallogenic features

The Lece-Chalkidiki zone is part of the Serbo-Macedonian metallogenic province as a larger metallogenic unit (Fig. 1). Pol- ymetallic deposits are the basic metallogenic feature of the zone. Examinations per- formed defined various morphogenetic types among which hydrothermal lead-zinc and porphyry copper deposits are dominant (Table 1 and 2). Antimony vein and metasomatic lead and zine (01ympias type) deposits are also dominant. In order to get a mo- re complete view of the metallogentic features of individual deposits in the Lece- Chalkidiki zone the paper will give a detailed account of individual features of lead- zinc and porphyry copper deposits.

Lead and zine are two prevailing ore metals in the zone under consideration discovered in many deposits and occurrences ha- ving various specific characteristics. In the Table 2 is given summary of the most signi-

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Table 2. Metallogenic characteristics of the Pb-Zn deposits in the Lece-Chalkidiki zone Deposit Kiseljak Buchim Borov Dol Vathi Pontokerasia Skouries Host rock Andesite Gneiss/

Andesite Andesite Brecciated

rhyodacite Rhyodacite/

Granosyenite Granodiorite Porphyry Parent

igneous rock Subvolcanic

stock/andesite Subvolcanic

stock/andesite Rhyodacite

dyke/Subvolcanic Subvolcanic

stock/dyke. Stock; Granod Absolute age,

my 12-23 25-28 24-28 30 32 29.6

Horizontal

projection 0.24 km^z 0.25 km^z 0.15 km^z 150x700 m 300x400 m

200x400 m 100x200 m

Vertical 300-500 m 250 m 300 m 500 m 700 m

Hydrothermal

alteration Biot,Ser,Sil,Pyr, Arg,Ch,Ty,Di,Cd Cr

Pot,Biot,Ser,Sil,

Ch Pot,Biot,Ser,Sil,

Arg,Ch,Ep,Ca Pot,Biot,Ser,Sil Ser,Sil,Ch,Ar,Pyr Pot,Ser,Arg,Ch Association of

minerals Cy,Py,Mgt,Mo, Au,T,Ga,Sp,E,Bi 0.3 % Cu 0.3 ppm Au 1.0 ppm Ag 23 ppm Mo 4-10% pyrite

Cy,Py,Mgt,Au, He,B,Bi,E,Ga, Sp,Te,Ag,Pd

Cy,Py,Mgt,He,

Mo,Au,B,Sp Cy,Py,B,E,Ga,Sp,

Mgt,He Cy,Py:Stockwork

diss,Ga,Sp,Veins Cy,Py,B,Au,Mgt Sp,Ga,T 0.3 % Cu

0.6 ppm Au 1.1 ppm Ag 13 ppm Mo 1 -4 % pyrite Traces:Pd,Se,Te

0.3 % Cu 0.3 ppm Au 0.35 ppm Ag 20 ppm Mo Main Consti-

tuents of ore 0.3 % Cu

0.25 ppm Au 150 ppm Ag 24 ppm Mo 2 % pyrite

0.3 % Cu 0.15 ppm Au 0.35 ppm Ag 20 ppm Mo

0.5 % Cu 0.7 ppm Au 2.5ppm Ag Traces: Pd,Te,Pt Cy-chalcopyrite; Py-pyrite,B-bomite

Ga-galena; Sp-sphalerite; Mgt-magnetite He-hematite; T-tetrahedrite; E-enargite Bi-bismuthine; Au-native gold; Ag-silver min.

Pot-potassium; Biot-biotitization; Ser-sericitization; Sil-silification;

Agr-argilization; Ch-chloritization (proipilitic); Gr-greizenization;

(topaz,cassiterite, wolframite); Ep-epidotization; Ca-carbonatization Pyr-pyritization; Ty-turmalinization; Di-diaspor; Cd-corundum

Table 3. General features of the porphyry copper deposits in the Lece-Chalkidiki zone Deposit Novo Brdo Farbani Potok Zletovo Blizanci 01ympias Host rock Andesite,

Breccias Dacite, Andesite Andesite, Dacite, Andesite,

Ignimbrite Ignimbrite

Quartzlatite Granodiorite Parent igneous Subvolcanic

intrusion/andesite Subvolcanic intrusion/dacite, andesite

Subvolcanic

dyke/andesite Subvolcanic dyke/dacite, andesite

Subvolcanic

dyke/quatzlatite Subv.intrus /granodiorite

Absolute age, 29.2 27.5 25.5 26.5 27 29.6

Horizontal

projection 5.2 km 5 km 2 km 6 km 2.5 km' 4.2 km

Vertical extent 800 m 300 m 800 m 1000 m 350 m 800 m Hydrothermal

alteration Sil,Pyr,Kaol, Lim Biot,Ser,Sil, Ch Biot,Ser,Sil,

Arg,Ch,Ep,Ca Sil,Kaol,Ser, Sil,Kaol,Ser, Sk,Ep,Ser, Sil,Ca Association of

minerals Ga,Sp,Py,Cy,

T, Au, Ga,Sp,Py,Pi,

Cy,T Ga,Sp,Py,Cy,

Pi,T Ga,Sp,Py,Cy,

T,E,Mgt,He Ga,Sp,Py,Cy,T Ga, Sp, Py, Apy, Cy,T,E Main Consti-

tuents of ore 1.5-2.5% Pb

3- 5% Zn 4- 7 g/t Au

15-30 g/t Ag

1-5 % Pb, 1-8% Zn, 18% Mn 3-4 g/t Au 100 g/t Ag

4 -12 % Pb 2-30 % Zn 150 g/t Ag

5.90 % Pb 2.07% Zn 0.01 % Cd 44 g/t Ag

5.5 % Pb 2.61 % Zn

40 g/t Ag

3.5 % Pb 4.5 5 Zn 2.48 % As 6-7 g/t Au 130 g/t Ag Mineral

potential 800 000 t Pb+Zn 30 t Au 2001 Ag

500 000 t Pb+Zn 400 0001 Mn

15 t Au 4501 Ag

500 000 t Pb+Zn

750 tAg 2.5000001 Pb+Zn

1300 tAg 150 000 t Pb+Zn

70 tAg 1.500000t Pb+Zn 400 000 t As

901 Au 2 0001 Ag Cy-chalcopyrite; Py-pyrite,Apy-arsenopyrite

Ga-galena; Sp-sphalerite; Mgt-magnetite He-hematite; T-tetrahedrite; E-enargite Au-native gold; Ag-silver min, Pi-pyrrhotite

Biot-biotitization; Ser-sericitization; Sil- Pyr-pyritization; Lim-limonitization; Sk- Ca-carbonatization; Ch-chloritization.

■silification; Kaol-kaolinization;

•skamization; Ep-epidotization;

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ficant metallogenetic features of the largest lead-zinc deposits in the zone. The table in- dicates that almost ali deposits are associa- ted with volcano-intrusive facies of Terti- ary volcanism. Most of them have large horizontal strike in the mineralized area, the vertical range of mineralization exceeding 1000 m. Ali ore deposits possess complex mineral associations with galena and sphalerite as dominant minerals. Minerals contents are of interest in some deposits such as the gold contents in the Leče and Ol- ympias deposits. The Zletovo is a typical vein type deposit, whereas 01ympias is of hydrothermal metasomatic type. The ore mineralization in the Leče deposit is loca- ted within the silicified fracture zones. In addition to hydrothermal lead-zinc deposits, porphyry copper deposits discovered are also of interest. The basic metallogenetic features of this type of deposits, simi- larly to those already described, are shown in Table 3. The Table shows that they are low grade porphyry deposits of small horizontal and vertical range. Almost ali porphyry deposits mentioned are in direct con- nection with subvolcanic dykes and stocks of the Tertiary igneous rocks. On average the copper content amounts to 0.3% except for the Skouries deposit. Gold content is also low except for the Buchim and Skouries deposits. A common feature of ali deposits is the presence of various kinds of hydrothermal alterations which is a specific feature of porphyry copper deposits. It should also be mentioned that these deposits re- present a specific group of porphyry deposits mainly connected with small subvolcanic intrusions. Besides the lead-zinc and copper deposits mentioned, skarn iron, epi- thermal arsenic and antimony, hydrother-

mal uranium etc. deposits are also determi- ned in the zone. Compared with those described earlier, however, their significance, in terms of the metallogeny and economic interest, is much lower.

Conclusion

The Lece-Chalkidiki metallogentic zone under consideration represents a very im- portant metallegentic segment in the geolo- gical composition in the south parts of the Balkan peninsula. It is essentally characterized by lineament structures, Neogene volcano-intrusive magmatism and polymetal- lic mineralization. Lead, zine and copper followed by gold, antimony and arsenic are the dominant ore metals in the whole zone.

The most significant mineral deposits are lead-zinc veins and metasomatic types as well as porphyry copper deposits.

References

Arsovski , M. Silvanov,! 1977: Neotec- tonies, magmatism and metallogeny on the teri- tory of Yugoslavia. In: S. Jankovič, (ed.) Metallo- geny and Plate Tectonics in the NE Mediterrane- an. -Fac.Min.Geol., 471-482.

Jankovič, S., Petkovič, M., Tomson, I. N. & Kr a v c o v, V. 1980: Porphyry copper deposits in the Serbo-Macedonian province, Sou- theastem Europe. -SGA-Spec.publ.N°l, 96-102.

Papadakis.A. & Michalidis,K. 1976:

Hydrothermal alteration for porphyry copper type mineralization in the subvolcanic rocks at Eastern Chalkidiki, Greece. - Sci. Ann. Fac.

Phys. Math., 16, 452-474.

Serafimovski, T. 1993: Structural-Me- tallogenic Features of the Lece-Chalkidiki zone:

Types of Mineral Deposits and Distribution. - Faculty of Mining and Geology., Spec.issue N°.

2., 328p.